High pitched whistle sound from IAC valve. - Ford Explorer Forum - Forums for Ford Explorer Enthusiasts
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Old 01-11-2017, 01:35 PM   #1
sport40
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High pitched whistle sound from IAC valve.

Hi; im getting a whistle sound from my IAC valve. like a vaccum leak, but i checked and there is no leaks around it, im wondering if its leaking internally? would this cause my engine miss fire code?

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Old 01-12-2017, 12:00 PM   #2
J_C
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First, this is not a "Performance Tuning" related question, rather general repair should be put in the appropriate subforum for your generation of vehicle.
http://www.explorertalk.com/forums/f35/

This also helps because you didn't mention your model year or which engine. Sometimes it doesn't matter but other times, you have to know the details to know it doesn't matter.

Trace all vac lines on the intake, that they're plugged in there and the other end of each line.

I suppose it's possible an IAC's internal airflow could whistle, but calling it a leak, well sort of as it could need cleaned out. Pull it off and generously spray carb or intake cleaner on it, let it sit, spray some more and use a cotton swab or similar to clean off the plunger hat inside where it seals against the cavity on the IAC body. It's spring loaded so you may need a pick or needle nose pliers to hold the plunger down to get access to it.

If your IAC also has a plastic cap on the side, gently pry it off and rinse out the two felt filter pads in it with solvent, and shoot some solvent down in the hole that those cover, and again shake out excess solvent.

After cleaning and shaking out excess cleaning solvent, I like to put a drop of motor oil on the shaft where it meets the bushing, and prop up the whole IAC so that gravity causes the oil to seep into the bushing, leaving it like that for a few hours before reinstalling on the vehicle.

While the IAC is off, note the state of the bottom. On some if not all engines there is a silicone rubber gasket. It and the mating surface on the IAC body should be clean. Some might have a paper gasket too which isn't really needed if the silicone gasket is intact, but if it's there it is another source of a leak and probably shouldn't be reused.

About the misfire. Pull the OBDII codes, look them up and post them here. Is it only one cylinder? If so you might pull the spark plug and take a look, just to verify it's in good shape and what it looks like, and you could confirm that you're getting spark on it while engine is running. You might have a waste spark system on the (whichever?) engine such that if one plug isn't making spark, the opposing bank plug on the same ignition coil won't make spark either.

The OBDII codes could be important to note other things like running too lean. Perhaps you have an intake manifold leak. Running without the (electric) cooling fan plugged in, or belt off a mechanically driven fan, (for only a few minutes at most so it doesn't overheat), you can use a cigar to smoke test the intake for leaks, or spray starter fluid or carb cleaner, etc to see if it seems like a particular area of the intake is leaking.

Try not to drive it much until fixed, excess unburnt fuel resulting from misfire can ruin a catalytic converter if exposed to it for too long. So far I've only mentioned leaks since you mentioned the whistle sound. Once a vehicle gets older there could be more than one thing wrong or a sound is just a coincidence.

For example you could have a clogged fuel injector causing misfire and just observed the whistle because you started looking at the engine closer, or even a warped intake, warped head, cracked head or cylinder wall. These are less likely unless there was an extreme overheating situation but might be detected with a cylinder compression test or leak down test.

Sometimes its easiest to try the simple quick things first. For example if it seems like IAC is leaking, see if the bolts for it have worked loose, but otherwise I'd start with pulling the OBDII codes.
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Old 01-12-2017, 12:33 PM   #3
sport40
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Jc, ive been over entire car, it has a high pitched whistle sound coming from the iac valve. ive cleaned it and it actually got worse...lol. will iac cause a miss code? i know on my 88 5.0 fox, it caused the car to run rough. my ex is a 2001 4.0 sohc, car very much babied. came from california.
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Old 01-12-2017, 02:41 PM   #4
J_C
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I think it's more likely an intake leak. Didn't you state that you replaced the gaskets? Assuming that was done well, then I'd wonder if your upper intake is plastic and has a crack in it, or warped, and the whistle sound is just being created NEAR the IAC, not from it. It can be hard to pinpoint exact location of high frequency noise, BUT, if the IAC is really clean inside and this is an external air leak, spraying some carb cleaner at the gap and having it sucked in, should affect the engine.

When all else fails, you start over as if you never touched anything, in case something was overlooked. Oh, and the intake gaskets, sometimes intake will need re-torqued after they compress a little, but do be sure to use a torque wrench again.

Sometimes cleaning the IAC is not enough, it has worn too much and needs replaced. However if it is sticking and you didn't add a drop of oil to the shaft, work it up and down into the bushing and let it sit to soak into bushing, at least I would try that before replacing it.
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Old 01-12-2017, 03:51 PM   #5
sport40
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Hi; yes new gaskets, checked manifold surface nice and flat, i used a whole can of carb cleaner and have found no vaccum leaks, i found the whistle from the iac using a mechanics stethiscope to locate noise.
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